C# - MakeNiceSize()

/// <summary>
        /// Calculates a good Looking file size
        /// </summary>
        /// <param name="size">Your size in Bytes</param>
        /// <returns>String, value not greater 1024, with unit</returns>
        public static String MakeNiceSize(double size)
        {
            return MakeNiceSize(size, "auto");
        }

        /// <summary>
        /// Calculates a good Looking file size
        /// </summary>
        /// <param name="size">Your size in Bytes</param>
        /// <param name="mode">Any of "auto","B","KB","MB","GB","TB","PB","EB"</param>
        /// <returns>String, value with unit</returns>
        public static String MakeNiceSize(double size, string mode)
        {
            string[] Suffix = new string[]{"B", "KB", "MB", "GB", "TB", "PB", "EB"};
            int run = 0;

            if (mode=="auto")
            {
                while (size >= 1024)
                {
                    size /=1024;
                    run++;
                }
            }
            else if(mode != "auto")
            {
                if (Suffix.Contains(mode))
                {
                    while (Suffix[run] != mode)
                    {
                        size /=1024;
                        run++;
                    }
                }
                else
                {
                    return "ERROR: Unknown mode";
                }

            }
            return Math.Round(size,2).ToString("00.00") + " " + Suffix[run];
        }